Long term investors are basically money lenders who expect a certain amount of "interest" (there have been money lenders for ages, I don't know how primitave you want to go). But even in hunting/gathering times, I'm sure there was still some dude who lent out his spear in return for a slab of meat.

Short term investors, who take advantage of small market fluctuations, could be compared to merchants, who take advantage of price differentials by region. Basically they are people who barter for something only to want to barter it again for even higher returns, taking advantage of need for the good of both parties. I doubt this was applicable on anything but the most minor scale in small tribal villages, but as soon as you have a society, especially multiple large groups, it starts to be more relevant/necessary.

If you take anything out of that, it's that short and long term investors need to be classified separately.